Current medical treatment for human kidney failure includes kidney transplant, hemodialysis and peritoneal dialysis. In hemodialysis therapy, the patient's vasculature is accessed using needles, catheters or implanted artificial or surgically created arterial-venous shunts. Using such-apparatus, whole blood is removed from the body and routed through an ex-vivo dialysis filter which removes catabolic and metabolic toxins by diffusion to a liquid medium or dialysate. The filtered blood is returned to the body via the access devices. Such hemodialysis is commonly performed 2-4 hours per day, 2-3 times per week resulting in a high and low blood toxin concentrations of the patient with attendant periods of trauma.
In peritoneal dialysis heretofore, using a batch process, a catheter is surgically placed in a patient's peritoneal cavity between the parietal peritoneum and the visceral peritoneum. Dialysate fluid is infused into the peritoneal cavity for a dwell time deemed adequate for being equilibrated, by diffusion, with the blood contained in the surrounding peritoneal membrane vasculature. The toxins in the patient's blood diffuse through the peritoneal membrane into the dialysate and the resulting toxin laden dialysate is then drained from the peritoneal cavity and either discarded or regenerated. Such a batch process cycling is repeated using new or fresh dialysate which is infused into the patient's peritoneum.
The peritoneal membranes act as a plasmapheresis filter which passes blood components and fluids below 10.sup.5 daltons from the vasculature in the membranes to the peritoneal cavity. A major disadvantage of the batch peritoneal dialysis process is that it not only removes the undesirable uric acid, urea and creatinine toxins along with other blood toxins having a molecular weight of less than 10.sup.5 daltons, but also many desirable proteins and other blood and plasma components. Of special concern is the removal of albumin which has a molecular weight of 6.9.times.10.sup.4 as well as a number of other important and desirable blood components. Removable of substantial or excessive amounts of albumin requires replacement in order to avoid hypoalbuminemia. The expense of such albumin replacement is often quite high. In addition, the aforesaid batch peritoneal dialysis process also removes important immune system proteins. Another major disadvantage of the batch dialysis process is that each treatment requires breaking the sterile bacterial and viral barrier between the patient's body and ex-vivo thereby substantially increasing the risk of infection and contamination each time dialysis fluid is added or removed. Yet another disadvantage of the batch process is the inefficiency of the dialysis/time ratio in the process cycle since dialysis occurs only 30 minutes out of each 70 minute cycle with the remainder 40 minutes spent draining toxic dialysate and infusing fresh dialysate. It is to the elimination of such disadvantages that the present invention is directed.